This invention relates to a process for preparing mixtures of polyalkylenepolyamines and alkanolpolyamines.
Mixtures of polyalkylenepolyamines and alkanolpolyamines find utility in the formation of urethane polymers. Typically, polymers produced with these mixtures exhibit rates of polymerization which are different from the rates produced with either alkanolpolyamines or polyalkylenepolyamines alone. Since the physical properties of urethane polymers can vary with rate of polymerization, a broader spectrum of polymer properties is available from the use of mixtures of polyalkylenepolyamines and alkanolpolyamines.
It is known that polyalkylenepolyamines can be prepared by the reaction of an alkyl halide with ammonia or an amine. The product is a polyalkylenepolyamine hydrohalide salt, which must be neutralized with base in order to recover the valuable polyalkylenepolyamine product. Disadvantageously, the neutralization produces a waste stream of metal salt, which must be removed. More disadvantageously, the process does not coproduce alkanolpolyamines. Even more disadvantageously, the process producess considerable amounts of undesirable cyclic compounds, such as piperazine.
It is known that salt-free non-cyclic polyethylenepolyamines can be directly prepared by reacting ammonia with an ethanolamine in the presence of hydrogen and a hydrogenation catalyst. For example, U.S. Pat. No. 3,766,184 discloses such a process with catalysts of nickel, iron, and cobalt supported on a variety of supports, including inorganic silicates. U.S. Pat. No. 3,270,059 teaches the amination of alkanediols and alkanolamines with primary or secondary amines to diaminoalkanes in the presence of Group IB and Group VIII metals in admixture with carrier substances, such as synthetic or natural silicates. These processes produce only the lower polyalkylenepolyamines, and in certain examples substantial quantities of cyclics, such as piperazine. Disadvantageously, the process does not coproduce the higher homologues of polyalkylenepolyamines and the corresponding alkanolpolyamines.
More recently it is known to prepare non-cyclic polyalkylenepolyamines directly by reacting an alkanolamine with an alkyleneamine under non-reductive conditions, that is, in the absence of hydrogen. Many of the non-reductive aminations are known to employ a phosphorous containing catalyst. U.S. Pat. No. 4,555,582, for example, teaches the use of a thermally activated pelleted catalyst composition comprising zirconium silicate having phosphorous deposited thereon for the reaction of ethylenediamine with monoethanolamine. These processes do not coproduce significant amounts of higher molecular weight alkanolpolyamines. For instance, the triethylenetetramine fraction does not contain the corresponding hydroxy compounds, such as hydroxyethyldiethylenetriamine. Moreover, the phosphorus-component of these catalysts can leach into the reaction causing catalyst deactivation and separation problems.
Other non-reductive processes are known employing phosphorus-containing catalysts. U.S. Pat. No. 4,463,193, for example, discloses the production of non-cyclic polyalkylenepolyamines by reacting an alkanolamine with an alkyleneamine and ammonia in the presence of a Group IIIB metal acid phosphate, including the rare earth lanthanide metals. These processes do not coproduce significant quantities of higher molecular weight alkanolpolyamines. Moreover, the phosphorus-containing catalysts lose their physical integrity in the presence of water, which is a by-product of the amination reaction. In addition, the catalysts can react with water to release free phosphoric acid or amine phosphate salts, thereby losing their phosphorus component. Consequently, these catalysts can plug reactors or leach into the reaction mixture causing catalyst losses and separation problems.
Currently, therefore, the preparation of mixtures of polyalkylenepolyamines and alkanolpolyamines is a multi-step process. Consider, for instance, how one skilled in the art would prepare a mixture of triethylenetetramine and hydroxyethyldiethylenetriamine. First, triethylenetetramine and diethylenetriamine would be prepared either independently or as a mixture by any of the above-identified processes. Next, the isolated diethylenetriamine would be reacted with ethylene oxide to prepare hydroxyethyldiethylenetriamine. Finally, the mixture of triethylenetetramine and hydroxyethyldiethylenetriamine would be prepared in the desired weight ratio.
It would be advantageous to have an amination process which produces mixtures of higher molecular weight polyalkylenepolyamines and alkanolpolyamines from lower molecular weight alkylenepolyamines and alkanolamines. It would be more advantageous if the process is accomplished in one-step and does not produce a waste stream of metal salts. It would be even more advantageous if the catalyst for such a process is insoluble in the liquid reactants. It would be most advantageous if the catalyst for such a process retains its physical integrity in the presence of water. Such a process would eliminate problems with catalyst leaching, reactor plugging, and catalyst separation. A process having all of these attributes would operate at a considerable cost advantage over current technologies required to prepare such mixtures.